1. Field of the Invention
The present invention relates to a color video printer, and more particularly to a color dry silver type color video printer using a color dry silver film on which a color printing is directly achieved, without using a copy sheet.
2. Description of the Prior Art
Conventionally, there have been known various methods for printing images based on electrical video signals, on hard copies. For example, they include an inkjet type wherein dye jets are injected from nozzles, to produce a pictorial image, a bubble type wherein dye is heated to form bubbles which are, in turn, pricked off to produce a pictorial image, a thermal transfer printing type and a cycolor type.
Color video printers of the thermal transfer printing type and the cycolor type mainly conventionally used will be described.
Referring to FIG. 1, there is illustrated a conventional thermal transfer printing type color video printer. As shown in FIG. 1, this color video printer comprises a drum 1, a thermal transfer printing head 2, and a film case 5 disposed between the drum 1 and the thermal transfer printing head 2 and carrying a film 5a therein. A copy sheet 3 is fed between the film 5a and the drum 1. In FIG. 1, the reference numeral denotes a guide plate for guiding the copy sheet 3.
In operation of the color video printer, an electrical video signal is converted into a heat by the thermal transfer printing head 2 and then heat transferred to the copy sheet 3 via the film 5a so that a pictorial image is developed on the copy sheet 3. As shown in FIG. 2, the film 5a carried in the film case 5 has three color portions, that is, a yellow portion, a cyan portion and a magenta portion. Accordingly, printing is repeatedly performed for individual colors at the same position of the copy sheet 3, so as to achieve a color printing.
On the other hand, FIG. 3 illustrates a cycolor type color video printer. As shown in FIG. 3, the color video printer comprises a film supply reel 7 for supplying a cycolor film 6 which is fed from the film supply reel 7 along guide rollers 11a and 11b. The color video printer also comprises a fiber optics cathode ray tube (FOCRT) 10 for exposing an optical image to be printed, to the cycolor film 6 fed thereto along the guide rollers 11a and 11b. In the vicinity of the FOCRT 10, an urging device 9 is disposed which is adapted to urge the cycolor film 6 against an exposure surface of the FOCRT 10 to be in close contact therewith. Downstream of the guide roller 11b, a copy sheet supply device 12 is disposed to supply a copy sheet 3 beneath the cycolor film 6 which has completed its exposure to the FOCRT 10 and passed the guide roller 11b. The color video printer also comprises pressure development rollers 13 for applying a certain pressure to both the cycolor film 6 and the copy sheet 3 fed beneath the cycolor film 6 to develop an image on the cycolor film 6 onto the copy sheet 3, a take-up reel 8 for winding the cycolor film 6 fed from the pressure development rollers 12 via a guide roller 11c, separately from the copy sheet 3, and thermal fixing rollers 14 for heating the copy sheet 3 separated from the cycolor film 6 by a heater (not shown) to thermally fix the image on the copy sheet 3.
In operation of the cycolor type color video printer, the cycolor film 6 is taken out of the supply reel 7 and then fed to the exposure surface of the FOCRT 10 along the guide rollers 11a and 11b. By the urging device 9, the cycolor film 6 comes into close contact with the exposure surface of the FOCRT 10. Thereafter, the cycolor film 6 is exposed at its cycolor dye-coated surface to an image to be printed, by the FOCRT 10. The image exposure is sequentially carried out by lines while the cycolor film 6 is fed. After an exposure to one frame image is completed, the copy sheet 3 is supplied from the copy sheet supply device 12 beneath the image-exposed surface of the cycolor film 6. Accordingly, the cycolor film 6 passes through the pressure development rollers 13 while overlapping with the copy sheet 3. By the pressure development rollers 13, the cycolor dye portion on the cycolor dye-coated surface of the cycolor film 6 corresponding to a latent image formed by the image exposure is broken and smeared on the copy sheet 3, to develop the image. The cycolor film 6 is then wound around the take-up reel 8. On the other hand, the copy sheet 3 passes through the thermal fixing rollers 14 so that the pictorial image thereon may be thermally fixed. Thereafter, the copy sheet 3 is discharged out of the printer.
In the above-mentioned thermal transfer printing type color video printer, the picture quality is dependant on the thermal transfer printing head 2. For obtaining a good picture quality, however, a very expensive one should be used as the thermal transfer printing head 2. Since the thermal transfer printing head 2 repeatedly comes into close contact with and separates from the film 5a during the printing operation, this color video printer involves a drawback of a noise generated upon the movements of the thermal transfer printing head 2.
On the other hand, the cycolor type color video printer requires a relatively high pressure for breaking cycolor particles so that the latent image formed by the exposure of the cycolor film is transferred to the copy sheet. As a result, the size and weight of the pressure development rollers used for the development affect greatly the overall system. Where the FOCRT is used as an image exposure source, there is a problem of a bulk size of the overall system due to the length of the CRT.
In both the thermal transfer printing type and the cycolor type, a copy sheet should be used, in addition to a film. Such a use of copy sheet requires a copy sheet supply device which causes the system volume and the cost to increase. Since the image is developed via the film, the picture quality is degraded.